1. Field of the Invention
The present invention generally relates to centrifugal blowers. More particularly, the invention relates to a centrifugal blower having reduced noise generation.
2. Description of Related Art
Centrifugal fans or blowers, also known as scroll-type blowers, are utilized in a wide variety of applications where efficient movement of air is required, including HVAC systems for automobiles and office buildings.
One problem with existing blowers is the noise generated by the interaction between the airflow and the smooth inner surface of the blower housing. As air flows over the smooth surface, a thin boundary layer is formed which tends to adhere to the surface, due to viscosity, and flows smoothly over the surface, known as laminar flow. However, the presence of skin friction tends to slow down the laminar flow, causing it to grow thicker. Eventually, separation occurs and the flow becomes turbulent. As a consequence of this flow separation, aerodynamic sounds are generated. Flow separation noise is a major source of noise generation in the flow-induced sound of a centrifugal blower. This problem occurs most prominently along the cutoff due to the reduced cross-sectional area of the air passageway within the scroll section. Thus, the fluid-structure interaction at the cutoff is the major noise source in centrifugal blowers.
Centrifugal blowers are notorious for these extraneous sounds produced while the blower is in operation. Many people find these sounds to be unpleasant and annoying. Thus, there is a need in the art for an improved centrifugal blower having reduced flow-induced noise generation.